A recording method using an inkjet method is widely used since the recording method enables recording of a high quality image on various kinds of substrate by ejecting ink in droplet form from several nozzles that are placed in an inkjet head.
In image formation by an inkjet method, there is a case of using an image forming method in which an ink including a colorant is brought into contact with a treatment solution including a compound configured to aggregate components in the ink to form an image. Such an ink and a treatment solution are together used as an ink set.
For example, an ink set which includes an ink composition including resin particles and a pigment, and a treatment solution including an organic acidic compound having a specific structure, is proposed (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2013-18948). It is reported that an image with suppressed graininess can be formed by using this ink set.
An ink set which includes an ink composition including a pigment and water, and a treatment solution including a water-soluble high molecular compound, an organic acidic compound, silicone oil, and water is proposed (for example, see JP-A No. 2013-72045). It is reported that, by using this ink set, not only uneven coating of the treatment solution can be suppressed but also an image with suppressed graininess can be formed.
In addition to the above, there is, for example, an ink set in which a solution for promoting image recording, which is a treatment solution for improving permeability of an ink to a substrate, is combined with an ink.
For example, an ink set which includes a recording solution (ink) and a solution for promoting image recording including a surfactant having a specific structure, a compound for thickening the recording solution, and a compound for insolubilizing a colorant is proposed (for example, see Japanese Patent Nos. 3640369 and 3583257).